1. Field of the Invention
The present invention relates to a method of manufacturing a semiconductor device in which a semiconductor chip is sealed. In particular, the invention relates to a method of manufacturing a leadless, resin sealed semi-conductor device, which can also be made small and thin capable of achieving smallness and slimness.
2. Description of the Related Art
A conventional semiconductor device, especially a leadless, resin sealed semiconductor device, is manufactured in such a manner that a semiconductor chip mounted on a surface of a printed circuit board made of glass epoxy, ceramic, or the like and a plurality of connecting electrodes formed on the surface of the printed circuit board are electrically connected to each other by metal wires, and an electrode layer formed on the other surface of the printed circuit board so as to oppose the connecting electrodes and the respective connecting electrodes are electrically connected to each other via a conductive material disposed in a through hole. Then, the semiconductor device is structured by sealing the semiconductor chip with epoxy resin or the like.
Alternatively, instead of using the printed circuit board made of glass epoxy, ceramic, or the like, a semiconductor device is manufactured through the following another procedure. A conductive metal is electrodeposited on a board whose surface is conductive and partly masked by resist to form a metal layer for mounting a semiconductor chip and board electrodes separately. After the semiconductor chip is mounted on the metal layer, electrodes on the semiconductor chip and the board electrodes are electrically connected to each other, a mounting portion for the semiconductor chip is sealed with a resin layer on the circuit board, and the board is peeled off, thereby obtaining a resin sealed body having a rear surface of the metal layer and that of the board electrodes exposed (for example, refer to JP 2002-9196 A (FIGS. 10 and 2)).
In the first manufacturing procedure of the semiconductor device, however, precision in position is demanded during the manufacture. The connecting electrodes on one surface of the printed circuit board and the electrode layer on the other surface should be accurately placed in position on both sides of the printed circuit board. In addition, secure electrical contact between the electrodes and the electrode layer should be made via through-holes without positional displacement. The demand for precision becomes a bottleneck for reduction in manufacturing costs together with increase in the number of manufacturing steps for formation of the through-holes and conductor printing on the printed circuit board, and it also becomes necessary to assign a certain area for forming the throughholes between multiple semiconductor chips which are arranged adjacent to each other on the printed circuit board. Further, a limitation is placed on the number of the semiconductor devices to be arranged and formed on one printed circuit board. Moreover, since resin sealing is conducted on the relatively thick printed circuit board to which semiconductor chips are mounted in this manufacturing method, the presence of the printed circuit board itself hinders smallness and slimness of the semiconductor device, and heat generated by the operation of the semiconductor chips easily tends to accumulate in the circuit board itself. The semiconductor device thus also has insufficient heat dissipation property.
In addition, the second manufacturing procedure involves peeling off the bonding between the molding resin and the board to expose the electrodeposition layer made of the conductive metal in forming external connecting electrodes. The electrodeposition layer is thus pulled by the board upon the peeling. Consequently, terminal strength is reduced in some cases, which means that the manufacturing method has an unwanted potential leading to lowering yield of the semiconductor device and reduction in reliability during device packaging.